Shafts are commonly used to rotationally support various rotatable components of a turbomachine. Generally, the turbomachine includes an internal component shaft to which a turbine wheel and/or compressor wheel may be mounted, and an output shaft that is configured to couple the turbomachine to an accessory, such as a gearbox. Both of the shafts extend at least partially through the turbomachine.
In many cases, the internal component shaft and output shaft rotate at different speeds during operation. To allow the two shafts to operate with one another, an overrunning clutch may be coupled therebetween. The clutch includes a bearing housing, an inner race, and a plurality of bearings disposed therebetween. Generally, the clutch is lubricated via oil that is circulated from a sump into the bearing housing.
In some turbomachine configurations, the output shaft extends through an end wall of the bearing housing. Generally, it is desirable to minimize or eliminate oil leakage along the rotating shaft and through the end wall of the bearing housing to confine circulatory oil flow to the interior of the bearing housing. In this regard, a wide variety of oil seal configurations have been proposed in efforts to overcome oil leakage problems. In one example, an annular groove has been formed in the rotatable shaft and an o-ring disposed therein. However, the high speed shaft rotation and other operating conditions in a typical turbomachine environment have generally precluded complete elimination of the oil leakage. In particular, high speed shaft rotation at high environmental temperatures tends to result in relatively rapid wear of seal structures, rapid compression set of elastomers and early onset of oil leakage.
Hence, there is a need for a system that minimizes oil leakage from the turbomachine. It is also desirable for the system to be operable during high speed shaft rotation. Moreover, it is desirable for the system to have an extended life.